Evans, A. S. and Vavilkin, T. and Pizagno, J. and Modica, F. and Mazzarella, J. M. and Iwasawa, K. and Howell, J. H. and Surace, J. A. and Armus, L. and Petric, A. O. and Spoon, H. W. W. and Barnes, J. E. and Suer, T. A. and Sanders, D. B. and Chan, B. and Lord, S. (2008) Off-nuclear star formation and obscured activity in the luminous infrared galaxy NGC 2623. Astrophysical Journal Letters, 675 (2). L69-L72. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:EVAapjl08
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New optical Hubble Space Telescope (HST), Spitzer Space Telescope, and XMM observations of the luminous infrared galaxy (LIRG) NGC 2623 are presented. This galaxy was observed as part of the Great Observatories All-sky LIRG Survey (GOALS). The prominent 3.2 kpc southern extension to the nucleus has been resolved by HST observations into ~100 star clusters, making it one of the richest off-nuclear concentrations of bright clusters observed in GOALS. The clusters have M_(F555W) ~-6.6 to -12.6 mag, which is within the magnitude range of Antennae galaxy clusters and in excess of 30 Doradus clusters at the high end. Their optical colors are primarily consistent with ages of ~1–100 Myr. Archival GALEX data show the off-nuclear region to be extremely bright in the far-ultraviolet, being equivalent in luminosity to the resolved nuclear region at 0.15 µm, but becoming less energetically significant at increasing wavelengths. In addition, [Ne v] 14.3 µm emission is detected with Spitzer IRS, confirming the inference from the X-ray and radio data that an active galactic nucleus (AGN) is present. Thus, the off-nuclear optical clusters are associated with a secondary burst of activity corresponding to a star formation rate ~0.1–0.2 M⊙ yr^(-1); the bulk of infrared (and thus bolometric) luminosity is generated via star formation and an AGN embedded behind dust within the inner kiloparsec of the system. If the infrared luminosity is primarily reprocessed starlight, the off-nuclear starburst accounts for <1% of the present star formation in NGC 2623.
|Additional Information:||© 2008 The American Astronomical Society. Received 2007 September 3; accepted 2008 January 24; published 2008 February 22. A. S. E. thanks G. Soutchkova, A. Gil de Paz, C. Mihos, J. Carpenter, J. Williams, J. Condon, D. Frayer, and F. Walter for useful discussions and assistance. Support for this work was provided by NASA through grant HST-GO10592.01-A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. This research has made use of NED, which is operated by the JPL, California Institute of Technology, under contract with NASA.|
|Subject Keywords:||galaxies: active; galaxies: individual (NGC 2623); galaxies: interactions; infrared: galaxies|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||15 Jul 2009 21:00|
|Last Modified:||26 Dec 2012 10:55|
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